I know there has been some confusion around the DST updates KB928338 and KB929120. Hopefully this will help. Yesterday, Dec 12 we released two time zone updates to WU, MU, WSUS and the catalog. The first of these updates, KB 928388, addresses 30 time zone changes for Windows Operating Systems, and most notably the changes in the US and Canada DST rules for 2007. This update was classified as optional for customers and companies who wish to deploy it now. While this update is being offered as optional now, once Outlook and Exchange tools are completed, so that all updates and tools can be run at the same time, we expect to change the classification of 928338 to high priority or critical. For more information please see: http://www.microsoft.com/windows/timezone/dst2007.mspx.
Yesterday we also released KB929120 to update the DST rules for the West Australia time zone. The State of West Australia recently introduced daylight saving time on a trial basis for the next three years. However, the law was passed after the Global time zone update (KB 928388) was developed and tested, so we could not include the W. Australia rules into the initial package. That means basically that KB929120 only updates the DST rules for the West Australia time zone, and as such, we classified it as a high priority or critical update available to clients that are set to any Australia time zone and that have OS's on any English locale. We decided on this high priority, critical update classification as these customers are the most likely to be affected by this change.
Additionally the update (KB929120) was also made available as an optional update for all other WSUS clients which are not in an Australian time zone, or that are in an Australian time zone but not running an OS with an English locale. Depending on synchronization options, WSUS Admins might see two updates for KB 929120, (as a few have already reported), a critical and an optional update. Both updates are identical, but the detection logic is based on the parameters indicated above. Approving the critical update for install will make the update available on ONLY clients set to any Australia Time Zone and which are on an English locale OS. Approving the optional update will make the udpate available to systems not in an Australian time zone, or that are in an Australian time zone, but not running an OS with an English locale.
Hope this helps - sorry for the lengthy post but want to make sure i address some of this confusion.